I've drawn all my life, but I'd like to give you some advice anyway. As well as studying form and shading and all that, you should spend time "scribbling" or "doodling", because an important part of drawing is that connection between your brain and your eye and your hand. Just lines and rows of lines, and convergences of lines, curved, straight, crosshatched, whatever. Do a few pages worth. Then do some forms and try to shade them along their tangents, remembering the loose feeling you had when you were scribbling. I hope that helps. And what I mean by along their tangents is, try not to shade at an obtuse angle, and follow the forms you are shading.